The present invention relates to a dehumidifying agent or drying agent, and more particularly, to a drying agent comprising an organometallic compound.
A drying agent conventionally used is an inorganic compound such as silica gel, Molecular Sieves (trade name for Linde Co.) calcium oxide, calcium chloride etc. Such a drying agent is used in the form of powder or particulate material.
Silica gel and Molecular Sieves are physical adsorption-type drying agents. Since water adsorbed thereby is driven off at high temperatures, they can not be used at high temperatures, but can be regenerated.
Calcium oxide and calcium chloride are chemisorption-type drying agents. Since water adsorbed thereby is not driven off at high temperatures, they can be used at high temperatures. However, they can not been regenerated.
When high dryness is required, more highly efficient chemisorption-type drying agents such as phosphorous pentoxide, barium oxide and so on are used. However, aforementioned drying agents are difficult to handle because of high reactivity, corrosivity, toxicity, etc. Since aforementioned inorganic drying agents are scattered and contaminate the environment because of being used in the form of powder or particulate, a prevention of dust is required.
Most of the conventional drying agents comprise a deliquescent inorganic salt, water-soluble polymer or hygroscopic resin or a mixture thereof, and are white. However, there are a few transparent drying agents. Therefore, when they are used for a drying agent for an organic electro-luminescent (hereinafter referred to as xe2x80x9corganic ELxe2x80x9d) device, they have the disadvantage that the device can not be observed through the drying agent.
Further, since the conventional drying agents are almost white and do not so definitely change color and state, they have disadvantages that the confirmation of moisture absorption effect can be hardly made or the measure of renewal of the drying agent can be hardly determined. In order to solve such disadvantages, a technology for a dehumidifying agent or drying agent has been proposed, which comprises a deliquescent inorganic salt powder, a gelling agent and a colored powder having an average particle size of 0.001xcx9c100 xcexcm, and which changes color and/or tone (for example, Unexamined Patent Publication (Kokai) No. 2001-46832.)
Therefore, the object of the present invention is to overcome the problems described above and to provide a drying agent capable of being used at high temperatures or extremely low humidity in a sealed container and confirming changes in color and/or tone of the drying agent due to the absorption of moisture.
According to the present invention, there is provided a drying agent formed of an organometallic compound illustrated by the formula (1) 
wherein, R1, R2 and R3 are selected from the group consisting of alkyl group, aryl group, cycloalkyl group, heterocyclic group and acyl group having at least one carbon atom, and M is a trivalent metal atom.
In another aspect of the present invention, there is provided a drying agent formed of an organometallic compound illustrated by the formula (2) 
wherein, R1, R2, R3, R4 and R5 are selected from the group consisting of alkyl group, aryl group, cycloalkyl group, heterocyclic group and acyl group having at least one carbon atom, and M is a trivalent metallic atom.
In still another aspect of the present invention, there is provided a drying agent formed of an organometallic compound illustrated by the formula (3) 
wherein, R1, R2, R3 and R4 are selected from the group consisting of alkyl group, aryl group, cycloalkyl group, heterocyclic group and acyl group having at least one carbon atom, and M is a quadrivalent metallic atom.
Optionally, the drying agent of the organometallic compounds is used in combination with an additional drying agent.
Optionally, the drying agent of the organometallic compounds is used in combination with an additional drying agent taking advantages of physical adsorption.
Optionally, the drying agent of the organometallic compounds is used in combination with an additional drying agent taking advantages of chemisorption.
Optionally, the drying agent of the organometallic compounds is used in combination with an additional drying agent taking advantage of the chemisorption and an additional drying agent taking advantage of the physical adsorption.
Optionally, the drying agent of the organometallic compounds is placed on an inner surface of the sealed container.
Optionally, the drying agent of the organometallic compounds is dispersed in a nonaqueous solvent and placed on an inside of the sealed container.
Optionally, the drying agent of the organometallic compounds includes a coloring agent.
According to the present invention, a film of drying agent can be formed by applying a solution of the drying agent formed of the organometallic compound to a place to be dried directly or by means of a supporting member, and drying the solution of the drying agent in a dried atmosphere. The film of drying agent thus formed is transparent and is capable of being seen through the drying agent. In one form of the present invention, a nonaqueous solution can be formed by mixing the organometallic compounds illustrated by the formulae (1), (2) and (3) as a drying agent with a nonaqueous solvent. The organometallic compounds illustrated by the formulae (1), (2) and (3) as a drying agent can be mixed with a coloring agent showing the rate of moisture absorption to form a drying agent containing the coloring agent which makes full use of the color development.
These and other objects and advantages of the present invention will be appreciated by those skilled in the art from the description given herein and the appended claims.